Automatic circuit breaker



Nov. 12, 1935. J ACHS 2,020,331

AUTOMATIC CIRCUIT BREAKER Filed Sept. 22, 1953 2 Sheets-Sheet l A5 1 1b n j, 45% I .fnvsntar: Jasqph 555/75 3 g) JIM fl/650v tarngy Nov. 12, 1935. J. sAcHs AUTOMATIC C IRCU IT BREAKER Filed- Sept. 22, 1935 2 Sheets-Sheet 2 71 Sachs Jhmntar: J0

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Patented Nov. 12, 1935 UNITED STATES PATENT OFFICE 2,020,331 AUTOMATIC omcorr BREAKER. Joseph Sachs, West Hartford, Conn.

Application September 22, 1933, Serial No. 690,585 H26 Claims. (01. 200-116) having an improved arrangement of parts which permits the handle to be positioned at the front of an insulating support and which permits the other parts of the circuit breaker mechanism to be positioned at the rear of the said support. This arrangement makes it possible to utilize the insulating supporting member as the front cover or panel of the circuit breaker, thus avoiding the necessity for a separate front cover or Another and a closely related object of the invention is to provide a circuit breaker which has at least two supporting and enclosing parts and which is so constructed that the front part is detachably supported on the rear part and carries all of the movable parts and also all of the main contacts.

In my copending application for Automatic circuit breakers, Serial No. 690,584, filed on even date herewith, I have disclosed insulating walls associated with the circuit breaker contacts and so arranged as to lie adjacent the path of movement of each movable contact and to substantially completely surround the said path. In this way the arc-formed gases are substantially completely controlled and are kept away from other parts of the circuit breaker. One of the objects of the present invention is to provide an alternative construction which also serves to substantially completely surround the path of movement of each movable contact, and which has certain specific advantages as will presently appear.

While I have referred to insulating walls completely surrounding the arcing zone, I nevertheless prefer to provide in one of the enclosing walls suitable vents which permit the gases to escape under control and guidance so that they can be suitably cooled and then discharged from the circuit breaker. A further object of the invention is to provide in association with the enclosing walls a suitable venting means which permits the gases to be discharged under proper control and guidance.

In order to still further minimize arcing it may under some conditions be desirable to provide conducting arcing electrodes, immediately adjacent' the path of movement of the movable contact so as to break up the are into a plurality of smaller arcs in series in the manner shown and described in my aforesaid Patent No. 1,812,848. In accordance with the present invention I am enabled to effect considerable economy of manufacture and to obtain other important advantages by associating the arcing elements directly with the vents through which the arc-formed gases are discharged.

Circuit breakers of the type to which the invention relates are well adapted to be used in connection with or as parts of panel board constructions, and another object of the invention is to provide in association with the circuit breaker 10 proper'an arrangement of electrical conductors which facilitates the mounting of the circuit breaker in a panel board construction and the electrical connection thereof with the panel 15 board bus bar.

sun further objects of the invention will be apparent from the following specification and claims.

In the accompanying drawings I have illustrated two embodiments of the invention which 20 are similar, although differing in certain im-- portant respects. It will be understood that the drawings are intended for illustrative purposes only and are not to be construed as defining or limiting the scope of the invention, the claims 25 forming a part of this specification being relied along the line 2-2 of Fig. 1. 35

Fig. 3 is a view similar to Fig. 2, but showing the movable contacts in their open-circuit position while the handle is retained in closedcircuit position.

Fig. 4 is a rear view of the main unit of the circuit breaker, the movable parts being in the open-circuit positions.

Fig. 5 is a fragmentary transverse sectional View taken along the line 55 of Fig. 3.

Fig. 6 is a fragmentary side view of one of the side plates of the contact carrying member.

Fig. '7 is a longitudinal sectional view taken along the lines 'l'| of Figs. 1 and 8 and showing not only the main front unit but also lnterthe main along the line 88 of Fig. '7. but having the upper right hand portion thereof taken along the line li -B of Fig. 7:

Fig. 9 is a front view of the intermediate insulating member.

Fig. 10 is a. longitudinal sectional view of the intermediate insulating member taken along the line III-I0 of Fig. 9.

Fig. 11 is a front view of the rear insulating member.

Fig. 12 is a longitudinal sectional view of the rear insulating member takenalong the line I2-I2 of Fig. 11.

Fig. 13 is a view similar to Fig. '7, but showing a circuit breaker particularly adapted for panel board use.

Fig. 14 is a front view of the circuit breaker shown in Fig. 13, the associated metal parts being omitted.

In Figs. 1 to 6 of the drawings I have shown separately the main front unit of a circuit breaker embodying the invention, this unit including all of the essential circuit breaker parts and being adapted to be combined or associated with other parts as will be presently explained. Figs. 7 and 8 show the same unit in combination with additional insulating members which will be later described in detail.

The main front unit comprises an insulating member or support I which serves to carry all of the operating parts of the circuit breaker and also the main stationary contacts. The front unit with its insulating support is adapted to be mounted on a suitably recessed supporting structure, and, as will presently appear, the unit is so constructed that the contacts and certain other parts are at the rear of the main rear plane of the insulating support and are adapted to be positioned within the recess in the supporting structure. The main front plane of the insulating support I is indicated at I and the main rear plane thereof is indicated at I. The insulating support I is shown as being a substantially rectangular block, but it will be understood that the shape of the member may be varied to suit requirements.

At the rear of the main rear plane of the insulating support I are two similar substantially stationary main contacts 2 and 3, which areconnected with the said support by means of more or less resilient bent conducting straps l and 5. The straps 4 and 5 may be formed of a good conducting material such as copper and they may be reinforced by supplemental strips 6 and 1 formed of spring steel. As shown in Figs. 1, 2 and 4 the conducting strap 4 engages with a conducting strap 8 positioned at the rear of the supporting member I. The straps 4 and 8 are held in engagement with each other and in position off the support I by means of screws 9 and I0. As shown in Figs. 4 and '7 the conducting strap 5 engages a conducting strap II also positioned at the rear of the support I. The straps 5 and I I are held in engagement with each other and in position on the support I by means of screws I2 and I3 similar to the before-mentioned screws 9 and III. The conducting straps 8 and II may advantageously extend in opposite directions as shown in the drawings. As shown in Figs. 1, 2 and 4 the strap 8 extends to the left end of the support where it is provided with a wire terminal I I in a suitable recess I5. The strap 8 may be additionally held in place by means of a screw I6. As shown in Figs. 4 and 7 the conducting strap II extends to the right end of the base I where it is provided with a wire terminal I I in a recess I8.

Carried by the insulating support I at least in part at the rear of the main rear plane thereof is a movable contact member carrying contacts adapted to engage and disengage the stationary switch contacts. While I do not so limit myself, the contact member is shown as being pivotally movable. Secured to the support I are two rearward projecting parallel metallic supporting plates I9, I9 which are held in place by means of screws 20, 20 extending through the support I and engaging flanges on the said plates. Carried by the said plates I9, I9 and extending transversely between them is a pivot pin 2 I. Pivotally mounted on the pin 2I is a contact carrying member which includes two parallel insulating plates 22, 22 suitably connected together to move as a unit and having aligned bearing apertures through which the pivot pin extends. The plates 22, 22 are connected together in part by means of a rivet 23 extending through a spacing bushing 24. Spacing bushings 25, 25 are provided on the pivot pin 2I to hold the plates 22, 22 in proper spaced relation with the metallic side plates I9, I9.

Movable electrical contacts 26, 26 project laterally from the side plates 22, 22 of the contact carrying member and are adapted to engage the stationary contacts 2 and 3 as shown in Figs. 2 and 3. Extending transversely between the two sides plates 22, 22 is an insulating bar 21 and the two contacts 26, 26 are extended inward through suitable openings 29 in the side plates so as to engage the bar 21 at the lower face thereof as shown in Figs. 3 and 5. Each of the aforesaid openings 28 in the side plates 22 is shaped as shown in Fig. 6, each opening having a relatively wide portion and a relatively narrow portion. The wider portion of each opening is of sufflcient width to permit the corresponding contact 26 to be moved therethrough. Each contact 26 is notched at 26, the portion thereof between the notches being of such width as to be adapted to enter and fit the narrower portion of the corresponding opening 28. When the two contacts have been put in place as described with the narrower portions thereof entered at the narrower portions of the openings 28, the transverse insulating bar 21 is put in place with the ends thereof extending into and filling the wider portions of the openings 28. The inner portions of the contacts are then connected with the transverse insulating bar 21 by means of rivets 29, 29. Thus, the transverse insulating bar by extending into the openings 28 serves to lock the contacts in place in the narrower parts of the openings, and it also serves indirectly, by reason of its connection with the contact members, to assist in holding the plates 22, 22 in their proper spaced relation.

The entire contact carrying member is biased toward the left, that is, toward its open-circuit position as shown in Figs. 2 and 3 by means of a coil spring 30 surrounding one of the bushings 25. Movement of the contact carrying member is limited by engagement of the side plates 22, 22 directly with a rearward projection I on the support I, as shown in Fig. 3.

There is provided a movable member 3| which I will term an actuator or actuating member, this member serving as the means for moving or actuating the contact member for normal switching purposes or to eifeet closing of the circuit after automatic opening thereof. The actuator 3| is pivotally mounted on the pivot pin 2I between I provide an electro-responsively releasable mechanical connection between the actuator and thecontact carrying member, which connection is preferably an electro-responsive bi-metallic thermal strip 32 adapted to be deflected by reason of the heating action of excess current therein in accordance with the well known action of such bi-metallic strips. The strip 32 is substantially U-shaped, and has the legs thereof connected by means of the aforesaid rivets 29, 29-

rotatable roller 34. The thermal strip 32 carries a pin 35 which projects inwardly and which is adapted to normally engage the roller 34, as clearly shown in Fig. 2. As shown, the pin 35 projects. inward with respect to its path of arcuate movement. At normal temperatures the strip 32 serves'to mechanically connect the contact carrying member and the actuator, but when the bi-meta lic strip is heated by reason of the pascage of excess current therethrough it is deflected outward as shown by dot-and-dash lines in Fig. 2. so'as to cause the pin 35 to disengage the roller 34 and-permit the contact member to move under the-influence of the spring 30 in the clockwise direction to the position shown in Fig. 3 so as to separate the contacts 26, 26 from the contacts 2 and 3 and thus break the circuit.

For manually operating the actuator 3| I providea handle member 36 which projects forward through an opening in the support I so as to be manually engageable at the front of the front plane of the support. The said handle is preferably carried directly by the two side plates I9, l9. As shown in Figs. 2, 3 and '7 there is provided a transverse pivot pin 31 upon which the handle member 36 is rotatably mounted, this pivot rod being connected at its ends with the two side pates. The handle is held in central position on the pin by means of spacing bushings 38. The handle is biased for movement in the counter-clockwise or circuit-opening direction by means of a coil spring 39 surrounding one of the bushings. Links 40, 40 serve to connect the handle member 36 with the actuator 3|, these links being located at the sides of the hande member and between the side, members 3|, 3| of the actuator. They are connected with the handle member by means of a pivot pin at 4| and they are connected with the actuator by means of a pivot pin at 42.

When the parts are in the relative positions shown in Fig. 2 the links 40 cooperate with the handle member itself to form a toggle action which locks the parts in position with the movable contacts 26, 26 pressed into firm engagement with the stationary contacts 2 and 3. Continued movement of the hand e in the clockwise direction is prevented by the engagement of an extension 38 thereon with the pivot pin 2|, as shown in Fig. 2. The pivotal axis at 4| is at the left of a straight line connecting the pivotal axes at 31 and 42 and thus the handle member and the links 46 serve to resist the tendency of the contact member to move in the clockwise direction under the influence of the spring 36 and the resilient strips supporting the contacts. At the same time the toggle action holds the handle member in its upper closed-circuit position, resisting the tendency of the spring 39 to move it in the counter-clockwise direction.

The above described toggle action can be released by pressing the handle toward the left, the parts then moving under the action of the springs 30 and 39 to the relative positions shown in Fig. 7. The movable contacts 26, 26 are thus disengaged from the stationary contacts 4 and and the circuit is broken at two separate places. By moving the handle toward the right the several parts can be restored to their relative positions as shown in Fig. 2 and the circuit can be reestablished.

As already explained, the thermal strip 32 is adapted to be deflected outward upon the passage of excess current therethrough with the result that the pin 35 is disengaged from the roller 34. When this occurs the contact member moves automatically to the position shown in Fig. 3, this movement not being in any way dependent upon the handle and the actuator. In fact the handle may be held in the position shown in Fig. 3 without in any way interfering with the automatic releasing action. It will be understood however that, as already explained, the handle is ordinar'iy held in its closed-circuit position by reason of pressure transmitted through the links 40. As soon as the thermal strip is released fromits engagement with the actuator, this pressure through the links 40 is instantly released, and the handle member and the actuator immediately move' to their open-circuit positions whereupon the pin 35 is again engaged with the roller 34 as shown in Fig. 7. Movement of the handle member and actuator to their open-circuit positions occurs substantially simultaneously with the movement of the contact member. The parts can be restored to their closed-circuit positions as shown in Fig. 2 by merely moving the handle toward the right.

Preferably the circuit breaker parts are enclosed partly by the insulating member and partly by one or more other members at the rear which serve to support the member As shown there are two supporting and enclosing members 43 and 44. It will be observed that the circuit breaker mechanism except the handle, and that the conducting parts except the wire terminals, are all completely enclosed by the enclosing structure which comprises the three insulating membore 43, 44 and The member not only supports the mechanism and other parts, but also serves as a front cover, thus making it unnecessary to provide any separate cover.

The insulating member 43 is at the rear, an the insulating member 44 is directly engaged and supported by the member 43. The before-mentioned front insulating support or member directly engages with and is supported by the member 44. The two insulating members 43 and 44 are suitably recessed to permit the described movements of the contact carrying member and the contacts thereon. The member 44 is further formed with a recess 44 to receive the rearward projection Won the member The three insulating members may be connected in any suitable manner, and for this purpose I have shown screws 45, 45 extending through suitable holes in the members and provided at the rear with flanged nuts 46. The rear member 43 may be provided withsuitable holes such as 41, 41 for the reception of screws serving to secure the entire circuit breaker to a suitable support.

In accordance with one phase of the present invention there are insulating walls adjacent four sides of the path of movement of each movable contact, thus completely surrounding the said path, as set forth in my said application Serial No. 690,584. One of the said insulating wall: consists of the adjacent surface or wall 22*- of the corresponding insulating plate 22 forming a part of the contact carrying member. The other three walls are stationary, being formed on the members 43 and 44 as will now be described. At the sides of the recess in the member 43 are walls 48, 48 which are parallel to the plates 22, 22 and which are closely adjacent the paths of movement of the movable contacts 26, 26. The recess in the member 43 is further formed with rear arcua-te walls 49, 49 which are closely adjacent the paths of movement of the said movable contacts 26, 26 and positioned radially outward therefrom. The intermediate member 44 is formed with inward projecting cheek pieces 50,, 50 which are formed respectively with arcuate walls 5|, 5| closely adjacent the paths of movement of the movable contacts 26, 26 and positioned radially inward therefrom. From an inspection of Fig. 'I it will be seen that when the movable circuit breaker parts are in open-circuit positions, the intermediate member can be assembled with the front member I or separated therefrom without any interference between the cheek pieces 50, 50 and the movable contacts 26, 26. Assembly or separation is not possible with the parts in closedcircuit positions.

It will be apparent that, when the several parts are in assembled relation as shown in Figs. '1 and 8, the path of movement of each movable contact 26 is surrounded on four sides by the corresponding insulating walls 22 4B, 49 and 5|. Thus the said walls serve to very efiectively confine any are formed gases. It will be observed that the contacts 26, 26 are positioned substantially parallelly with their directions of movement, so that they engage at their edges with the stationary contacts 2 and 3. This provides narrow areas of engagement between the contacts which is desirable, and it has the additional advantage that the two surfaces 49 and 5| can be much closer together than would otherwise be posible. In this way the cross-sectional area of the passageway defined by the walls 22, 48, 49 and 5| is greatly reduced.

In order that the are formed gases may be released from the arcing zone and suitably cooled before being discharged, the insulating member 43 is formed with vents 52 extending rearward from the arcuate surfaces 49. I have shown four vents 52 associated with each contact, but it will be understood that I do not limit myself as to any particular number of vents. The vents of each series communicate with a corresponding duct extending longitudinally of the member 43 and communicating with the exterior thereof. As shown there are two ducts 53 and 54 having forward extensions 53 and 54 at opposite ends of the circuit breaker. As a matter of structural convenience the ducts 53 and 54 are initially open at the rear and are closed by an insulating plate 55 which may be held in place by the flanges on the nuts 46. It will be apparent that the are formed gases confined by the aforesaid walls-22, 48, 49 and 5| can escape through the vents 52, 52 and the ducts 53 and 54. In passing through the vents and ducts the gases become cooled so that upon their discharge through the outlets 53 and 54 they are sufficiently cooled to avoid any possible fire hazard.

In order to still further minimize arcing, one

or more arcing electrodes may be provided adja-- cent the paths of movement of the movable contacts 26, 26. In accordance with the invention these electrodes are provided in combination with the vents and are preferably located therein. 5

These electrodes may be variously formed, but they may be conveniently and economically provided in the form of thin plates or strips of such size and shape as to fit the several vents 52, 52. These strips 56, 56 are forced into the several 10 vents from the rear and they are held in place by means of the aforesaid insulating plate 55. It will be understood that the strips 56, 56 are of different lengths so that their forward or inner ends are closely adjacent the arcuate path 0115 contact movement. These electrodes 56, 56 serve to break up the are as explained in my aforesaid Patent No. 1,812,848.

In Figs. 13 and 14 I have shown a circuit breaker which is or may be identical in construction with that shown in Figs. 1 to 12 so far as concerns the main contacts and the mechanism and also so far as concerns the insulating parts for confining and controlling the are formed gases. The construction differs, however, in that the electrical arrangement and certain structural details are somewhat different in order to facilitate the use of the circuit breaker in or as a part of a panel board.

The front insulating member 51 is in the main similar to the front insulating member l, but is adapted to cooperate with the front wall 58 of a panel box. The recesses I5 and It! for wire terminals are omitted, as are also the holes for the connecting screws 45, 45. The insulating members 59 and 60 are in the main similar respectively to the insulating members 43 and 44, but differ in some details. The member 59 may be secured to the rear wall 56 of the panel box by means of screws 63, 63. The rear member 59 has gas vents and ducts similar to those already described. I have shown two ducts 64 and 65 which are similar to the ducts 53 and 54, but which differ in minor details.

The member 59 has an extension at the right which is formed with a transverse groove 6| at the rear for receiving a bus bar 62. Suitably mounted in recesses in the rear member 59 is a conductor 66 which is electrically connected with the strips carrying the contact 3 by means of a rod 61 threaded at both ends. The rod 61 will be recognized as taking the place of the screw |3 shown in Fig. 7. The conductor 66 is connected by means of the screw 66 with a button or plug 69 projecting forward from the bus bar 62. It will be apparent that through the several electrical connections described the contact 3 is electrically connected with the bus bar 62. Connected with the stationary contact 2 of the circuit breaker is a conducting strap 1|) shorter than the strap 8 shown in Figs. 2 and 4, but otherwise similar. By means of a rod 1| similar to the rod 61 already described the strap 16 is connected with a conductor 12 mounted in recesses in the rear member 59 and provided with a wire terminal 13. It will be observed that with the construction shown in Figs. 13 and 14 the electrical terminals are on the rear member instead of on the front member.

What I claim is: 70

1. In an automatic circuit breaker, the combibination of a supporting and enclosing structure comprising a front insulating support detachably mounted on the remainder of the said structure and serving as a front closure therefor, a contact carrying member movably mounted on the front support at the rear thereof and including a movable contact, a stationary contact on the support engageable by the movable contact, a handle movably mounted on the support having a manually engageable portion at the front of the support, and an electro-responsively controlled movable mechanical connection on the I support interposed between the handle and the contact carrying member, the said mechanicalnation of a supporting and enclosing structure.

comprising 'a front insulating support detachably mounted on the remainder of the said structure, a contact carrying member movably mounted on the front support at the rear thereof and including a movable contact, a stationary contact on the support engageable by the movable contact, an actuator movably mounted on the supcuit position.

port at the rear thereof, an electro-responsively controlled movable mechanical connection on the support interposed between the actuator and the contact carrying member normally enabling the former to move the latter and serving upon the attainment of an abnormal current condition in the circuit to disconnect the contact member from the actuator and to thereby permit the said member to move automatically and independently to its open-circuit position, and a movable handle on the support operati'vely connected with the actuator and having a manually engageable portion at the front of the support.

3. In an automatic circuit breaker, the combination of an insulating support, a contact carrying member movably mounted on the support at least in part at the rear of the rear main plane thereof and including a movable contact, a statlonary contact on the support at the rear of the rear main plane thereof and engageable by the movable contact, a handle movably mounted on the support and having a manually engageable portion at the front of the front planeof the support, and an electro-responsively controlled means carried by the support and normally constituting a part of a mechanical connection between the handle and the contact carrying member to normally enable the latter to move the former, the said electro-responsively controlled means acting upon the attainment of an abnormal current condition in the circuit to release the contact member from the control of the handle and to thereby permit the said member to move automatically and independently to its open-cir- 4. In an automatic circuit breaker, the combination of an insulating support, a contact carrying member movably mounted on the support at the rear of the main rear plane thereof,-an actuator movably mounted on the support at least in part-at the rear of the main rear plane there.- of and normally adapted to move the contact carrying member to open or close the circuit, an electro-responsive means comprising an element inherently responsive to abnormal current conditions in the circuit and normally constituting at least a part of a movable mechanical connection between the contact carrying member and the actuator, the said element upon the attainment of an abnormal current condition in the circuit and by reason of its own inherent electroresponsive characteristics being relatively movable to render the said mechanical connection ineffective and to thereby permit the contact carrying member to move automatically and independently to its open-circuit position, and a movable handle on the support operatively connected with the actuator and having a manually engageable portion at the front of the front plane of the support.

5. In an automatic circuit breaker, the combination of an insulating support, a movable contact carrying member pivotally mounted on the support at the rear of the main rear plane thereof, an actuator pivotally mounted on the support at least in part at the rear of the main rear plane thereof and normally adapted to move the contact carrying member to open or close the circuit, a bodily movable thermostatic bi-metallic strip serving in and of itself as a releasable latch normally mechanically connecting the contact carrying member with the actuator, the said latch being connected in the circuit so as to be automatically deflected upon the attainment of an abnormal current condition therein and to thus mechanically disconnect the contact carrying member from the actuator and permit it to move automatically andindependently to its open-circuit position, and a movable handle on the support operatively connected with the actuator and having a manually engageable portion at the front of the front plane of the support.

"the attainment of an abnormal current condition in the circuit to disconnect the contact member from the actuator and to thereby permit the said member to move automatically and independently to its open-circuit position, stationary insulating means associated with the contacts and comprising walls closely adjacent three sides of the path of movement of the movable contact, and an insulating wall movable with the contact member adjacent the said path of movement at the fourth side thereof.

'7. The combination in an automatic circuit breaker, of two stationary contacts, two movable electrically connected contacts adapted to engage and disengage the respective stationary contacts','the last said contacts being biasedfor movement in the circuit-opening direction and being normally held mechanically against such movement, an electro-responsive element bodily movable with the movable contacts and electrically connected between them to'be energized upon the attainment of an abnormal current condition in the circuit and serving when so energized to mechanicallly'release the said contacts a and thus permit them to automatically move to open-circuit positions, stationary insulating means associated with the contacts and comprising walls closely adjacent three sides ofthe path of movement of each movable contact,- and two insulating walls movable with the respective movable contacts adjacent the respective paths of movement at the fourth sides thereof.

8. An automatic circuit breaker comprising in combination, two stationary contacts, a movable contact carrying member having two flat contacts projecting transversely therefrom in opposite directions, the said contacts'being positioned on the contact member substantially parallelly with their directions of movement so as to be adapted to engage at their edges with the respective stationary contacts, electro-responsive means normally holding the contact member with its contacts in the contact engaging position and arranged to be energized upon the attainment of an abnormal current condition in the circuit so as to release the said contact member and permit it with its contacts to automatically move in the contact disengaging direction, and insulating means associated with the contacts and comprising opposite walls closely adjacent the paths of movement of the opposite flat facesof the movable contacts.

9. An automatic circuit breaker comprising in combination, two stationary contacts, a contact carrying member pivoted for movement about a transverse axis and having two fiat contacts projecting transversely therefrom in opposite directions, the said contacts being positioned on the contact member substantially parallelly with their directions of movement so as to be adapted to engage at their edges with the respective stationary contacts, electro-responsive means normally holding the contact member with, its contacts in the contact engaging position and arranged to be energized upon the attainment of an abnormal current condition in the circuit so as to release the said contact member and permit it with its contacts to automatically move in the contact disengaging direction, and insulating means associated with the contacts and comprising convex and concave walls closely adjacent the paths of movement of the opposite fiat faces ofthe movable contacts.

10. An automatic circuit breaker comprising in combination, two stationary contacts, a movable contact carrying member having two contacts projecting transversely therefrom in opposite directions and adapted to engage and disengage the respective stationary contacts, electroresponsive means normally holding the contact member with its contacts in the contact engaging position and arranged to be energized upon the attainment of an abnormal current condition in the circuit so as to release the said contact member and permit it with its contacts to automatically move in the contact disengaging direction, and two separate insulating members having a combined opening within which the contact member and contacts move which insulating members are formed respectively with walls closely adjacent the respective paths of movement of the movable contacts and respectively positioned inward and outward therefrom.

11. An automatic circuit breaker comprising in combination, two stationary contacts, a contact carrying member pivoted for movement about a transverse axis and having two contacts projecting transversely therefrom in opposite directions and adapted to engage and disengage the respective stationary contacts, electro-responsive means normally holding the contact member with its contacts in the contact engaging position and arranged to be energized upon the attainment of an abnormal current condition in the circuit so as to release the said contact member and permit it with its contacts to automatically move in the contact disengaging direction, and an insulating member having a central opening within which the contact member and its contacts move which insulating member includes two opposite inward projecting cheek portions formed with convex walls concentric with the respective paths of movement of the movable contacts and positioned radially inward therefrom.

12. An automatic circuit breaker, comprising in combination, an insulating member, two stationary contacts on the insulating member, a movable contact carrying member mounted on the insulating member and having two contacts projecting transversely therefrom in opposite directions and adapted to engage and disengage the respective stationary contacts, electro-responsive means normally holding the contact member with its contacts in the contact engaging position and arranged to be energized upon the attainment of an abnormal current condition in the circuit so as to release the said contact member and permit it with its contacts to automatically move in the contact disengaging direction, and a second insulating member removably connected with the first insulating member and having a central opening within which the contact member and contacts move which second insulating member includes two opposite inward projecting cheek portions formed with walls adjacent the respective paths of movement of the movable contacts and positioned inward therefrom, the relationship between the said cheek portions and the movable contacts being such that the second insulating member with its cheek portions can be removed from the first insulating member when the movable contacts are in their disengaged positions.

13. An automatic circuit breaker, comprising in combination, an insulating member, two stationary contacts on the insulating member, a contact carrying member mounted on the insulating member for pivotal movement about a transverse axis and having two contacts projecting transversely therefrom in opposite directions and adapted to engage and disengage the respective stationary contacts, electro-responsive means normally holding the contact member with its contacts in the contact engaging position and arranged to be energized upon the attainment of an abnormal current condition in the circuit so as to release the said contact member and permit it with its contacts to automatically move in the contact disengaging direction, and a second insulating member removably connected with the first insulating member and having a central opening within which the contact member and contacts move which second insulating member includes two opposite inward projecting cheek portions formed with convex walls concentric with the respective paths of movement of the movable contacts and positioned radially inward therefrom, the relationship between the said cheek portions and the movable contacts being such that the second insulating member with its cheek portions can be removed from the first insulating member when the movable contacts are in their disengaged positions.

14. An automatic circuit breaker comprising in combination, two stationary contacts, a contact carrying member pivoted for movement about a transverse axis and having two contacts projecting transversely therefrom in opposite direcwalls concentric with the respective paths of movement of the movable contacts and positioned radially inward therefrom, and a separate insulating member formed with concave walls concentric with the respective paths of movement or the movable contacts and positioned radially outward therefrom.

15. In an automatic circuit breaker, the com-- bination of a stationary contact, a movable contact adapted to engage and disengage the stationary contact, the last said contact being biased for movement in the circuit-opening direction and being normally held mechanically against such movement, an electro-responsive element closely adjacent the rupturing position of the 1 contacts and bodily movable with the movable contact, the said element being arranged to be energized upon the attainment of an abnormal current condition in the circuit so as to mechanically release the said contact and thus permit it to automatically move to open-circuit position, stationary insulating means comprising walls closely adjacent three sides of the path of movement of the movable contact, and an insulating means movable with the movable contacts and comprising a wall adjacent the fourth side of the path of movement of'the movable contact,

.the said movable insulating means also serving to shield the electro-responsive element from the rupturing position of-the contacts.

16. In an automatic circuit breaker, the combination of a stationary contact, a movable actuator, a movable contact adapted to engage and disengage the stationary contact and biased for movement in the circuit-opening direction, the said movable contact being normally mechanically connected with the actuator to be moved thereby, an electro-responsive element closely adjacent the rupturing position of the contacts and bodily movable with the movable contact and with the actuator, the said element being arranged to be energized upon the attainmentof an abnormal current condition in the circuit so as to mechanically release the movable contact from the actuator, stationary insulating means comprising walls closelyadjacent three sides of the path of movement of the movable contact, and an insulating means movable with the movable contacts and comprising a wall adjacent the fourth side of the path of movement of the movable contact, the said movable insulating means also serving to shieldthe said electro-responsive elementfrom the rupturing position of the contacts.

17. In .an automatic circuit breaker, the combination of a stationary contact, a movable actuator, a movable contact adapted to engage and disengage the stationary contact and biased for movement in the circuit-opening direction, a thermally responsive bi-metallic strip closely adjacent the rupturing position of the contacts and bodily movable with the movable contact and electrically connected in the circuit, the said strip normally serving as a latch to mechanically connect the movable contact with the actuator and the said strip upon being heated by an abnormal current therein serving to mechanically release the said contact and thus permit it to automatically move to open-circuit position, stationary insulating means comprising walls closely adjacent three sides of the pathof movement or the movable contact, and an insulating means movable with the movable contacts and comprising a wall adjacent the fourth side of the path of movement of the movable contact, the said movable insulating means also serving to shield the said bimetallic strip from the rupturing position of the contacts.

18. In an automatic circuit breaker, the combination of two stationarycontacts, a movable actuator, two movable contacts adapted to engage and disengage the respective stationary contacts and biased for movement in the circuitopening direction, a thermally responsive bi-metallic strip closely adjacent the rupturing position of the contacts and bodily movable with the movable contacts and electrically connected between them, the said strip normally serving as a latch to mechanically connect the movable contacts with the actuator and the said strip upon being heated by an abnormal current therein serving to mechanically release the said contacts and thus permit them to automatically move toopen-circuit position stationary insulating means comprising walls closely adjacent three sides of the path of movement-of each movable contact, and an insulating means movable with the movable contacts and comprising walls adjacent the fourth side of the path of movement of each movable contact, the said movable insulating means also serving to shield the said bimetallic strip from the rupturing positions of the contact.

19. The combination in an automatic circuit breaker, of a stationary contact, a movable contact adapted to engage and disengage the stationary contact, the last said contact being biased for movement in the circuit-opening direction and being normally held mechanically against such movement, an electro-responsive element arranged to be energized upon the attainment of an abnormal current condition in the circuit so as to mechanically release the said contact and thus permit it to automatically move to open-circuit position, and stationary insulating means substantially completely enclosing the contacts and comprising walls closely adjacent and substantially completely surrounding the path of movement of the movable contact, the said insulating means having thereina series of vents communieating with the arcing zone of the contacts and extending outward therefrom and the said insulating means also having a duct communicating with all of the vents and extending to the exterior of the insulating means.

20. The combination in an automatic circuit breaker, or two stationary contacts, two movable electrically connected contacts adapted to engage and disengage the stationary contacts, the last said contacts being biased for movement in the circuit-opening direction and being normally held .mechanically against such movement, an electroresponsive element arranged to be energized upon the attainment of an abnormal current condition in the circuit so as to mechanically release the said movable contacts and thus permit them to automatically move to open-circuit positions, and

stationary insulating means substantially completely enclosing the contacts and including walls closely adjacent the path of movement of each movable contact, the said insulating means having therein two separate series of vents each communicating with the arcing zone of the corresponding pair of contacts and extending rearward therefrom and the said insulating means also having two ducts communicating with the respective series of vents and each extending longitudinally to an end of the insulating means.

21. The combination in an automatic circuit breaker, of a stationary contact, a movable contact adapted to engage and disengage the stationary contact, the last said contact being biased for movement in the circuit-opening direction and being normally held mechanically against such movement, an electro-responsive element arranged to be energized upon the attainment of an abnormal current condition in the circuit so as to mechanically release the said contact and thus permit it to automatically move to opencircuit position, stationary insulating means substantially completely enclosing the contacts and comprising walls closely'adjacent the path of movement of the movable contact, the said insulating means having therein vents communicating with the arcing zone of the contacts and communicating with the exterior of the said insulating means, and metallic arcing electrodes positioned in the said vents.

22. The combination in an automatic circuit breaker, of a stationary contact, a movable contact adapted to engage and disengage the stationary contact, the last said contact being biased for movement in the circuit-opening direction and being normally held mechanically against such movement, an electro-responsive element arranged to be energized upon the attainment of an abnormal current condition in the circuit so as to mechanically release the said contact and thus permit it to automaticallymove to open-circuit position, stationary insulating means substantially completely enclosing the contacts and comprising walls closely adjacent the path of movement of the movable contact, the said insulating means having therein vents communicating with the arcing zone of the contacts and communicating with the exterior of the said insulating means and the said insulating means also having a duct communicating with all of the vents and extending to the exterior of the insulating means, and metallic arcing electrodes positioned in the said vents.

23. In an automatic circuit breaker, the combination of a front insulating support, two stationary contacts on the support, a movable contact carrying member on the support having two contacts adapted respectively to cooperate with the stationary contacts, the said contact carrying member being biased for movement in the circuitopening direction and being normally held mechanically against such movement, an electro-responsive element carried by the support and arranged to be energized upon the attainment of an abnormal current condition in the circuit so as to mechanically release the contact carryingmember and permit it to automatically move independently to open-circuit position, separate insulating means at the rear of the front support and rigidly connected therewith, at least one electric terminal on the rear insulating means, and an electrical connection extending rearward from one of the stationary contacts to the said terminal.

24. In an automatic circuit breaker, the combination of a front insulating support, two sta tionary contacts on the support, a movable contact carrying member on the support having two contacts adapted respectively to cooperate with the stationary contacts, the said contact carrying member being biased for movement in the circuit-opening direction and being normally held mechanically against such movement, an electroresponsive element carried by the support and arranged to be energized upon the attainment of an abnormal current condition in the circuit so as to mechanically release the contact carrying member and permit it to automatically move independently to open-circuit position, separate insulating means at the rear of the front support and rigidly connected therewith, two electric terminals on the rear insulating means, and electrical connections extending rearward from the respective stationary contacts to the said terminals.

25. In an automatic circuit breaker, the combination of a front insulating support, a movable actuating member on the support, a movable handle on the support adapted for operating the actuating member having a manually engagcable portion accessible at the front of the support, two stationary contacts on the support at the rear thereof, a movable contact carrying member on the support at the rear thereof and having two contacts adapted respectively to cooperate with the stationary contacts, the said contact carrying member being biased for movement in the circuitopening direction and being normally mechanically connected with the actuating member, an electro-responsive element carried by the support and arranged to be energized upon the attainment of an abnormal current condition in the circuit so as to mechanically release the contact carrying member from the actuating member and thus permit it to automatically move independently to open-circuit position, separate insulating means at the rear of the front support and rigidly connected therewith, electric terminals on the rear insulating means, and electrical-connections extending rearward from the respective stationary contacts to the said terminals.

26. In an automatic circuit breaker, the com bination of a front insulating support, two stationary contacts on the support, a movable contact carrying member on the support having two contacts adapted respectively to cooperate with the stationary contacts, the said contact carrying member being biased for movement in the circuit-opening direction and being normally held mechanically against such movement, an electroresponsive element carried by the support and arranged to be energized upon the attainment of an abnormal current condition in the circuit so as to mechanically release the contact carrying member and permit it to automatically move independently to open-circuit position, separate insulating and enclosing means at the rear of the front support and rigidly connected therewith, the said means having a rear groove for receiving a bus bar, electric terminals mounted on the rear insulating means and enclosing means and one of them adapted for engaging a bus bar in the said groove, and electrical connections extending rearward from the respective stationary contacts to the said terminals.

JOSEPH SACHS. 

